1. Field of the Invention
This invention relates to a test instrument and, more particularly, to a test instrument in which, by way of example, the color reaction of various sampled specimens is measured automatically by a measuring device.
2. Description of the Prior Art
A multi-layered analytical sheet for liquid-sample analysis, in which quantitative measurement of a specific component of a specimen is performed in a simple manner, is disclosed in the specification of Japanese Patent Publication (KOKOKU) No. 61-61347. This multi-layered analytical sheet for liquid-sample analysis is disadvantageous in that the reaction time is long owing to structural limitations.
In view of this drawback, the applicant has proposed, in Japanese Patent Application No. 63-334198 entitled "Test Instrument", a test instrument exhibiting a shortened reaction time. In order to analyze a component contained in a specimen, this test instrument includes a light-transmissive support member on one surface of which is provided with a reagent layer and a spreading layer for uniformly spreading the specimen. The instrument is integrated by the pressing action of a holding member in such a manner that the spreading layer is situated on the outer side.
With the "Test Instrument" proposed by the applicant, the time needed for a sampled specimen to reach and soak the reagent layer is shortened and the permeability of a gas such as oxygen necessary for a color reaction is enhanced, thereby hastening the rate of the color reaction. On the other hand, the test instrument may be inserted into an insertion port of a test device and used together with the test device, which is adapted to measure the elapsed time of the color reaction.
FIG. 9 is a sectional view of the test instrument proposed by the applicant. This sectional view is broken away along a plane passing through the center of a circular opening in the instrument. As shown in FIG. 9, the test instrument, has a main body 200 in which an opening 200a of diameter d.sub.2 is formed. A cover 400 is integrally provided on the main body 200 as by bonding. The cover 400 is provided with an opening 400a of radius d.sub.1, which is approximately the same as diameter d.sub.2. The central axis of the cover 400 is made to coincide with a center line CL of the opening 200a in main body 200.
A light-transmissive layer 6 comprising a transparent resin material has a portion of its lower side exposed to the outside via the opening 200a. A reagent layer 8 for undergoing a color reaction with a specimen is provided on the upper surface of the light-transmissive layer 6. A liquid spreading layer 10 is disposed on the reagent layer 8, and a portion of the upper surface of the liquid spreading layer 10 is exposed to the outside via the opening 400a. The lower surface of the liquid spreading layer 10 is in contact with the reagent layer 8.
In accordance with this arrangement, a sampled specimen is developed by the liquid spreading layer 10 via the opening 400a, after which the specimen soaks the reagent layer 8 to cause a color reaction. This color reaction is measured by optical measuring means to obtain a measurement value. In order to perform this measurement, the opening 200a in the main body 200 is irradiated with light from a light-emitting element, the amount of reflected light, which varies in approximate proportion to the color reaction, is detected by a light-receiving element, and a change in the color reaction with time is measured. This method can be used to measure blood-sugar value, by way of example.
In this "Test Instrument" proposed by the applicant, the diameter of the opening 200a to the transparent light-transmissive layer 6 and the diameter of the opening 400a to the liquid spreading layer 10 are substantially the same, as mentioned above. Therefore, it is required that the specimen which has reacted with the reagent layer 8 be distributed uniformly over the entire area of the opening 200a to the light-transmissive layer 6 by spreading the specimen evenly over the entire area of the opening 400a to the liquid spreading layer 10. However, if too much of the specimen attaches itself at this time, the specimen cannot be distributed uniformly and the excess specimen, which has no place else to go, will drip from the instrument.
In addition, though it is necessary for the specimen which has reacted with the reagent layer 8 to be distributed uniformly over the entire area of the opening 200a to the light-transmissive layer 6, it is very difficult to uniformly distribute the specimen over such a wide area in this manner.